Modular connection for orthopedic component

ABSTRACT

An orthopedic component comprising a first element and a second element, with the first element and the second element being secured to one another with a modular connection, wherein the modular connection comprises a taper junction and an engaged-fit junction.

REFERENCE TO PENDING PRIOR APPLICATIONS

This patent application is a continuation of prior U.S. patentapplication Ser. No. 10/749,136, filed Dec. 30, 2003 now U.S. Pat. No.7,125,193 by Alfred S. Despres III et al. for MODULAR CONNECTION FORORTHOPEDIC COMPONENT, which in turn is a continuation of prior U.S.patent application Ser. No. 09/909,929, filed Jul. 20, 2001 now U.S.Pat. No. 6,669,728 by Alfred S. Despres III et al. for MODULARCONNECTION FOR ORTHOPEDIC COMPONENT, which in turn claims benefit of (i)prior U.S. Provisional Patent Application Ser. No. 60/219,955, filedJul. 20, 2000 by Alfred S. Despres III et al. for MODULAR ORTHOPEDICCONNECTION; and (ii) prior U.S. Provisional Patent Application Ser. No.60/219,963, filed Jul. 20, 2000 by Alfred S. Despres III et al. forFORCE COUPLE CONNECTION.

The above-identified patent applications are hereby incorporated hereinby reference.

FIELD OF THE INVENTION

This invention relates to surgical apparatus and procedures in general,and more particularly to orthopedic components.

BACKGROUND OF THE INVENTION

Orthopedic components are well known in the art.

For example, in joint replacement surgery, portions of a joint arereplaced with orthopedic components so as to provide long-lastingfunction and pain-free mobility. More particularly, in the case of aprosthetic total hip joint, the head of the femur is replaced with aprosthetic femoral stem component, and the socket of the acetabulum isreplaced by a prosthetic acetabular cup component, whereby to provide aprosthetic total hip joint. Similarly, in the case of a prosthetic totalknee joint, the top of the tibia is replaced by a prosthetic tibialcomponent, and the bottom of the femur is replaced by a prostheticfemoral component, whereby to provide a prosthetic total knee joint.

Orthopedic components are also used in a variety of other ways. Forexample, orthopedic components may be used to stabilize a fracturedbone, or to secure two vertebral bodies together, or to hold a bonegraft to a bone, or to secure soft tissue to a bone, etc.

In many situations, an orthopedic component may comprise two or moreelements which may need to be secured to one another. By way of example,in the case of a prosthetic total hip joint, the prosthetic femoral stemcomponent is sometimes constructed out of a plurality of separateelements, wherein each of the elements may be independently selected soas to most closely approximate patient anatomy, and wherein the separateelements may be assembled to one another using modular connections, soas to provide the best possible prosthetic femoral stem component forthe patient. Similarly, in the case of a prosthetic total knee joint,the prosthetic tibial component is also sometimes formed out of aplurality of separate elements which are assembled using modularconnections. Still other types of orthopedic components may require, ormay benefit from, the assembly of a plurality of separate elements usingmodular connections.

Once deployed in the patient's body, the orthopedic components, andhence the modular connections securing the separate elements to oneanother, are typically subjected to axial, bending and torsional loads.While different types of modular connections are known in the art, noone type of existing modular connection is ideal for dealing with allthree types of loads, i.e., axial, bending and torsional loads. By wayof example, taper connections generally accommodate axial (i.e.,compressive) loads well, but they generally do not accommodate bendingand torsional loads particularly well. By way of further example,concentric cylinder connections generally accommodate bending loadswell, but they generally do not accommodate axial and torsional loadsparticularly well.

SUMMARY OF THE INVENTION

As a result, one object of the present invention is to provide animproved modular connection for connecting together a plurality ofseparate elements so as to form an orthopedic component.

Another object of the present invention is to provide an improvedorthopedic component.

These and other objects are addressed by the provision and use of thepresent invention.

In one form of the invention, there is provided an improved modularconnection for connecting together a plurality of separate elements soas to form an orthopedic component, the improved modular connectioncomprising, in combination, a taper junction and an engaged-fitjunction.

In another form of the invention, there is provided an improvedorthopedic component comprising a first element and a second element,with the first element and the second element being secured to oneanother with a modular connection, wherein the modular connectioncomprises, in combination, a taper junction and an engaged-fit junction.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which are tobe considered together with the accompanying drawings wherein likenumbers refer to like parts and further wherein:

FIG. 1 is a schematic, exploded side view of one form of modularconnection formed in accordance with the present invention;

FIG. 2 is a schematic, exploded side view of another form of modularconnection formed in accordance with the present invention;

FIG. 3 is a schematic, exploded side view of still another form ofmodular connection formed in accordance with the present invention;

FIG. 4 is a schematic, exploded side view of yet another form of modularconnection formed in accordance with the present invention; and

FIG. 5 is a schematic, exploded side view of another form of modularconnection formed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Looking first at FIG. 1, there is shown an orthopedic component 5 formedin accordance with the present invention. Orthopedic component 5 maycomprise a prosthetic femoral stem component of the sort used in aprosthetic total hip joint and comprising a plurality of separateelements which are assembled using a modular connection; or orthopediccomponent 5 may comprise a prosthetic tibial component of the sort usedin a prosthetic total knee joint and comprising a plurality of separateelements which are assembled using a modular connection; or orthopediccomponent 5 may comprise any other type of orthopedic component whichmay require, or which may benefit from, the assembly of a plurality ofseparate elements using a modular connection.

Orthopedic component 5 generally comprises a first element 10 and asecond element 15. First element 10 includes an aperture 20 into whichportions of second element 15 extend.

In accordance with the present invention, first element 10 and secondelement 15 are adapted to be secured to one another using an improvedmodular connection 25 so as to form the complete orthopedic component 5.

More particularly, modular connection 25 comprises, in combination, twoload-bearing junctions: a taper junction 30 and an engaged-fit junction35.

Taper junction 30 is formed by the interaction of a first taper 40 witha corresponding second taper 45. More particularly, first taper 40 isformed on a projection 50 of second element 15. Second taper 45 isformed along a portion of the sidewall defining the first body element'saperture 20. First taper 40 and second taper 45 seat securely againstone another so as to together form the load-bearing taper junction 30.

The engaged-fit junction 35 is formed by the interaction of a firstconcentric wall 55 with a second concentric wall 60. More particularly,first concentric wall 55 is formed on projection 50 of second element15. Preferably first concentric wall 55 is disposed on projection 50coaxial with, and distal to, first taper 40. Second concentric wall 60is formed along a portion of the sidewall defining the first element'saperture 20. Preferably second concentric wall 60 is disposed on firstelement 10 coaxial with, and distal to, second taper 45. Firstconcentric wall 55 and second concentric wall 60 seat securely againstone another so as to form the load-bearing engaged-fit junction 35.

In general, the engaged-fit junction 35 is a mechanical connection thatachieves stability by the deformation of one member so that it ispressure locked against a constraining second member. This deformationcan be expansion (e.g., as in a taper expanded collet) or contraction(e.g., as in a force fit). The deformation can also be effected bythermal expansion or thermal contraction (e.g., as with a shape memoryalloy such as Nitinol or the like). Regardless of how the deformation isachieved, the resulting mechanical connection has surfaces which areforcefully engaged against one another as a result of the deformation,whereby to establish the engaged-fit junction.

As noted above, there are a number of ways in which first concentricwall 55 and second concentric wall 60 can be made to seat securelyagainst one another so as to form the load-bearing engaged-fit junction35.

For example, first concentric wall 55 can be made slightly oversizedrelative to second concentric wall 60, such that force fitting firstconcentric wall 55 internal to second concentric wall 60 will create theengaged-fit junction 35.

Alternatively, and in accordance with a preferred form of the presentinvention, the distal end of the second element's projection 50 may beformed with a recess 65, and the proximal end of third element 70 mayinclude a projection 75 for insertion into recess 65. More particularly,projection 75 is oversized relative to recess 65, such that insertion ofprojection 75 into recess 65 will cause a radial expansion of firstconcentric wall 55 into engagement with second concentric wall 60,whereby to create the engaged-fit junction 35. In one preferred form ofthe invention, recess 65 and projection 75 are both tapered, and thedistal end of second element 15 is a split collet. Alternatively, thedistal end of second element 15 may be formed out of a materialsufficiently resilient to engage second concentric wall 60 without beingsplit.

Due to the unique construction of modular connection 25, orthopediccomponent 5 is able to accommodate axial, bending and torsional loadsbetter than prior art devices. More particularly, modular connection 25simultaneously provides two load-bearing junctions: the taper junction30 and the engaged-fit junction 35. The taper junction 30 accommodatesaxial (i.e., compressive) loads extremely well. At the same time, theengaged-fit junction 35 accommodates bending and torsional loadsextremely well. Additionally, the engaged-fit junction 35 stabilizes thetaper junction 30 against bending and torsional loads. Together, the twoload-bearing junctions collectively handle axial, bending and torsionalloads significantly better than prior art devices.

Looking next at FIG. 2, there is shown an alternative form ofconstruction. Here, the aperture 20 comprises a blind hole formed infirst element 10, and third element 70 extends through an opening 80formed in second element 15 and communicating with recess 65, withengaged-fit junction 35 being actuated by pulling proximally on thirdelement 70 once first taper 40 has been seated against second taper 45.

Looking next at FIG. 3, there is shown another alternative form ofconstruction. Here, the taper junction 30 and the engaged-fit junction35 are disposed parallel to one another, rather than coaxial with oneanother as shown in FIGS. 1 and 2. To this end, aperture 20 comprises apair of parallel apertures 20, and projection 50 comprises a pair ofparallel projections 50.

Looking next at FIG. 4, there is shown still another alternative form ofconstruction. Here, the taper junction 30 and the engaged-fit junction35 are disposed coaxial and to at least some extent overlap with oneanother, rather than being axially separated in the manner shown in FIG.2.

Looking next at FIG. 5, there is shown yet another form of construction.Here, third element 70 is in the form of a ring and is used to drivesecond element 15 inward so as to effect the engaged-fit junction 35between first concentric wall 55 and second concentric wall 60.Preferably, this is effected by providing second element 15 with a tapersurface 85 and third element 70 with a corresponding taper surface 90.In use, first element 10 and second element 15 are brought together sofirst taper 40 engages second taper 45 and so that first concentric wall55 is adjacent to second concentric wall 60, and then third element 70is moved toward second element 15 so that the engagement of tapersurface 85 with taper surface 90 causes first concentric wall 55 tosecurely engage second concentric wall 60, whereby to actuate theengaged-fit junction 35.

It will be understood that many additional changes in the details,materials, steps and arrangement of parts, which have been hereindescribed and illustrated in order to explain the nature of theinvention, may be made by those skilled the art without departing fromthe principles and scope of the present invention.

1. An orthopedic assembly for a prosthetic component, the assemblycomprising: a first prosthetic element having a projection defined atleast in part by an outer concentric wall and an outer tapered wallaxially extending from an end of the outer concentric wall to a freeend; a second prosthetic element having a tubular body having aninternal concentric wall defining a free end and an internal taperedwall extending axially inward from an opposite end of the internalconcentric wall, said second element being adapted to receive said firstelement such that the tapered walls of said first and second elementsabut each other, and the concentric walls of said first and secondelements engage each other, said second element having an externaltapered surface disposed around the second element internal concentricwall and tapering towards the free end of the tubular body; and a thirdelement comprising a ring having an internal tapered surface axiallyextending from one end of the ring to the other end, which throughoutthe length of the ring is complementary to, and engageable only with,the second element external tapered surface; wherein said first andsecond elements engage with each other such that the first element outertapered wall abuts the second element internal tapered wall and thefirst element outer concentric wall engages the second element internalconcentric wall; and wherein said third element engages said secondelement such that said third element internal tapered surface engagesonly the second element external tapered surface, said third elementinternal tapered surface being a smaller diameter than said secondelement external tapered surface to cause the second element externaltapered surface and the second element internal concentric wall todeform redially inward and cause the second element internal concentricwall to deformably form a force fit with the first element outerconcentric wall, thereby securing said first and second elements to eachother.
 2. An orthopedic assembly according to claim 1 wherein said firstelement concentric wall is adapted to be located internally of thesecond element concentric wall.
 3. An orthopedic assembly according toclaim 2 wherein the second element concentric wall is deformable so asto be pressure locked against the first element concentric wall.
 4. Anorthopedic assembly according to claim 1 wherein the second elementconcentric wall is contractible so as to be pressure locked against thefirst element concentric wall.
 5. A method for effecting a jointreplacement surgery, the method comprising the steps of: providing anorthopedic assembly comprising: prosthetic a first element having aprojection defined at least in part by an outer concentric wall and anouter tapered wall axially extending from an end of the outer concentricwall to a free end; a second prosthetic element having a tubular bodyhaving an internal concentric wall defining a free end and an internaltapered wall extending axially inward from an opposite end of theinternal concentric wall, the second element being adapted to receivethe first element such that the tapered walls of the first and secondelements abut each other, and the concentric walls of the first andsecond elements engage each other, the second element having an externaltapered surface disposed around the second element internal concentricwall and tapering towards the free end of the tubular body; and a thirdelement comprising a ring having an internal tapered surface axiallyextending from one end of the ring to the other end, which throughoutthe length of the ring is complementary to, and engageable only with,the second element external tapered surface; wherein said first andsecond elements engage with each other such that the first element outertapered wall abuts the second element internal tapered wall and thefirst element outer concentric wall engages the second element internalconcentric wall; and wherein said third element engages said secondelement such that said third element internal tapered surface engagesonly the second element external tapered surface, said third elementinternal tapered surface being a smaller diameter than said secondelement external tapered surface to cause the second element externaltapered surface and the second element internal concentric wall todeform radially inward and cause the second element internal concentricwall to deformably form a force fit with the first element outerconcentric wall; and bringing together the first element and the secondelement so the first element outer tapered wall engages the secondelement internal tapered wall and such that the first element concentricouter wall is adjacent to the second element internal concentric wall;and moving the third element axially toward the second element so thatengagement of the third element internal tapered surface with the secondelement external tapered surface causes the second element concentricinternal wall to securely engage the first element outer concentricwall, thereby locking the second element onto the first element.